In order to achieve rational production of different watch models, manufacturers use the same timepiece movement model (also called a “calibre”) in a known manner, in combination with various display assemblies. Each of these assemblies includes the desired display members (hour, minute and seconds hands, date indicators, chronograph hands, etc.) and the gear trains necessary for driving these members from one or several mechanical outputs of the movement. This assembly is commonly called a “module”, because it is often meant to be able to be replaced by a different module in the same timepiece movement, called the “basic movement”.
For the purpose of varied production, the use of a distinct display module for the basic movement means, in particular, that an off-centre display device, for example a small seconds display, can be used, or the module can be changed to change the display type, for example a retrograde hand, or to add a display device, for example a 24 hour display, without the requirement to develop a new movement each time.
However, this type of module is devised for one or several predefined display functions and, if one wishes to produce a modified watch model, the display module evidently has to be modified, which involves re-engineering the module and complicating production and storage by increasing the number of component references.